Separator for lithium secondary battery and lithium secondary battery comprising same

Abstract

The present invention relates to a separator for a lithium secondary battery, and a lithium secondary battery including the same. The separator includes a porous substrate, and a coating layer on at least one surface of the porous substrate, wherein the coating layer includes a (meth)acrylic copolymer including a first structural unit derived from (meth)acrylamide, a second structural unit derived from (meth)acrylonitrile, and a third structural unit including at least one of structural units derived from (meth)acrylamidosulfonic acid, a (meth)acrylamidosulfonic acid salt, or a combination thereof; inorganic particles; and an organic filler; wherein the organic filler is included in an amount of 0.1 to 50 wt % based on a total amount of the organic filler and the inorganic particles.

The invention claimed is: 
     
       1. A separator for a lithium secondary battery, comprising
 a porous substrate and 
 a coating layer on at least one surface of the porous substrate, 
 wherein the coating layer comprises a (meth)acrylic copolymer including a first structural unit derived from (meth)acrylamide, a second structural unit derived from (meth)acrylonitrile, and a third structural unit including at least one of structural units derived from (meth)acrylamidosulfonic acid, a (meth)acrylamidosulfonic acid salt, or a combination thereof; 
 inorganic particles; and 
 an organic filler; 
 wherein the organic filler is included in an amount of 5 to 50 wt % based on a total amount of the organic filler and the inorganic particles, and 
 wherein 
 the first structural unit derived from (meth)acrylamide is included in an amount of 80 to 85 mol % based on 100 mol % of the (meth)acrylic copolymer, 
 the second structural unit derived from (meth)acrylonitrile is included in an amount of 10 to 15 mol % based on 100 mol % of the (meth)acrylic copolymer, and 
 the third structural unit derived from (meth)acrylamidosulfonic acid, (meth)acrylamidosulfonic acid salt, or a combination thereof is included in an amount of 5 to 10 mol % based on 100 mol % of the (meth)acrylic copolymer. 
 
     
     
       2. The separator of  claim 1 , wherein a volume ratio of the inorganic particle and the organic filler is 40:1 to 1:3. 
     
     
       3. The separator of  claim 1 , wherein a weight ratio of the (meth)acrylic copolymer:a sum amount of the organic filler and the inorganic particles is 1:20 to 1:40. 
     
     
       4. The separator of  claim 1 , wherein an average particle diameter of the organic filler is 0.1 to 0.5 μm. 
     
     
       5. The separator of  claim 1 , wherein an average particle diameter of the inorganic particles is 0.3 to 0.7 μm. 
     
     
       6. The separator of  claim 1 , wherein the organic filler is at least one organic compound selected from a (meth)acrylate-based compound and a derivative thereof, a diallyl phthalate-based compound and a derivative thereof, a polyimide-based compound and a derivative thereof, a copolymer thereof, and a mixture thereof. 
     
     
       7. The separator of  claim 1 , wherein the inorganic particles comprise Al 2 O 3 , SiO 2 , TiO 2 , SnO 2 , CeO 2 , MgO, NiO, CaO, GaO, ZnO, ZrO 2 , Y 2 O 3 , SrTiO 3 , BaTiO 3 , Mg(OH) 2 , boehmite, or a combination thereof. 
     
     
       8. The separator of  claim 1 , wherein the (meth)acrylic copolymer has a glass transition temperature of 130 to 160° C. 
     
     
       9. The separator of  claim 1 , wherein
 the first structural unit derived from (meth)acrylamide is represented by Chemical Formula 1, 
 the second structural unit derived from (meth)acrylonitrile is represented by Chemical Formula 2, and 
 the third structural unit derived from (meth)acrylamidosulfonic acid, (meth)acrylamidosulfonic acid salt, or a combination thereof is represented by one of Chemical Formula 3, Chemical Formula 4, Chemical Formula 5, and a combination thereof: 
 
       
         
           
           
               
               
           
         
         wherein, in Chemical Formula 1 to Chemical Formula 5, 
         R 1  is hydrogen or a methyl group, 
         R 2 , R 3 , R 4 , and R 5  are each independently hydrogen or a C1 to C3 alkyl group, 
         L 1 , L 3 , L 5 , and L 7  are each independently —C(═O)—, —C(═O)O—, —OC(═O)—, —O—, or —C(═O) NH—, 
         L 2 , L 4 , L 6 , and L 8  are each independently a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group, 
         x and y are each independently an integer of 0 to 2, 
         a, b, c, d, e, and f are each independently an integer of 0 to 2, 
         M +  is an alkali metal, and 
         * indicates a bond to an adjacent structural unit. 
       
     
     
       10. The separator of  claim 1 , wherein the (meth)acrylic copolymer has a weight average molecular weight of 200,000 to 700,000. 
     
     
       11. The separator of  claim 1 , wherein the (meth)acrylic copolymer is included in an amount of 1 wt % to 5 wt % based on a total amount of the coating layer. 
     
     
       12. The separator of  claim 1 , wherein the coating layer has a thickness of 1 to 5 μm. 
     
     
       13. A lithium secondary battery, comprising
 a positive electrode, a negative electrode, and the separator of  claim 1  between the positive electrode and the negative electrode.